Lithium-Ion Battery Separator with Dual Safety of Regulated Lithium Dendrite Growth and Thermal Closure by Assisted Assembly Technology

Lithium metal batteries offer a huge opportunity to develop energy storage systems with high energy density and high discharge platforms. However, the battery is prone to thermal runaway and the problem of lithium dendrites accompanied by high energy density and excessive charge and discharge. This study presents an assisted assembly technique (AAT) based on flexible barium titanate (BTO) and poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) nanofibers for preparation of a battery separator. AAT was used to combine the BTO diaphragms with high thermal stability and the PVDF-HFP diaphragms with good Elasticity and piezoelectricity, and the thermal stability was improved by 200 and 125% increase in battery cycle life compared to PVDF-HFP diaphragms alone. And demonstrated excellent thermal closure performance between 160 and 200 °C. Furthermore, the piezoelectric effect of the composite film prevents the growth of lithium dendrites in the vertical direction, avoiding the trouble of lithium dendrites penetrating the battery separator. Therefore, the two safety guarantee properties of the composite separator greatly enhance the safety and service life of the battery, which allows the application of lithium batteries to be further improved in the application scenario and application scale.